Photodynamic therapy (PDT) is a clinically approved, minimally invasive therapeutic procedure that can exert a selective cytotoxic activity toward malignant cells. The procedure involves administration of a photosensitizing agent followed by irradiation at a wavelength corresponding to an absorbance band of the sensitizer. In the presence of oxygen, a series of events lead to direct tumor cell death, damage to the microvasculature, and induction of a local inflammatory reaction. Clinical studies revealed that PDT can be curative, particularly in early stage tumors. It can prolong survival in patients with inoperable cancers and significantly improve quality of life. Minimal normal tissue toxicity, negligible systemic effects, greatly reduced long-term morbidity, lack of intrinsic or acquired resistance mechanisms, and excellent cosmetic as well as organ function-sparing effects of this treatment make it a valuable therapeutic option for combination treatments. With a number of recent technological improvements, PDT has the potential to become integrated into the mainstream of cancer treatment. CA Cancer J Clin 2011;61:250-281. V C

/pdf/photodynamic-therapy-of-cancer-an-update-4fcrlehb17.pdf

Photodynamic therapy of cancer: An update†‡

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

Biomedical Diagnostics. Edited by Tuan Vo-Dinh Edited by Tuan VoDinh. CRC Press 20142014. Pages 311–356. Print ISBN: 978-1-42008514-3. eBook ISBN:. Bjorn Kemper is a senior researcher at the Biomedical Technology Center of the Srirang Manohar is an associate professor of biomedical photonic imaging. This volume discusses biomedical photonics, spectroscopy and microscopy, the basic physical principles underlying the technology and its applications.

https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-9/issue-5/0000/Book-Review-Biomedical-Photonics-Handbook/10.1117/1.1776177.pdf

Biomedical Photonics Handbook

White blood cells (WBCs) are a major component of immunity in response to pathogen invasion. Neutrophils are the most abundant WBCs in humans, playing a central role in acute inflammation induced by pathogens. Adhesion to vasculature and tissue infiltration of neutrophils are key processes in acute inflammation. Many inflammatory/autoimmune disorders and cancer therapies have been found to be involved in activation and tissue infiltration of neutrophils. A promising strategy to develop novel targeted drug delivery systems is the targeting and exploitation of activated neutrophils. Herein, a new drug delivery platform based on neutrophils is reviewed. There are two types of drug delivery systems: neutrophils as carriers and neutrophil-membrane-derived nanovesicles. It is discussed how nanoparticles hijack neutrophils in vivo to deliver therapeutics across blood vessel barriers and how neutrophil-membrane-derived nanovesicles target inflamed vasculature. Finally, the potential applications of neutrophil-based drug delivery systems in treating inflammation and cancers are presented.

Neutrophil-Based Drug Delivery Systems

Photodynamic therapy (PDT) utilizes the destructive power of reactive oxygen species generated via visible light irradiation of a photosensitive dye accumulated in the cancerous tissue/cells, to bring about their obliteration. PDT activates multiple signalling pathways in cancer cells, which could give rise to all three cell death modalities (at least in vitro). Simultaneously, PDT is capable of eliciting various effects in the tumour microenvironment thereby affecting the tumour-associated/-infiltrating immune cells and by extension, leading to infiltration of various immune cells (e.g. neutrophils) into the treated site. PDT is also associated to the activation of different immune phenomena, e.g. acute-phase response, complement cascade and production of cytokines/chemokines. It has also come to light that, PDT is capable of activating ‘anti-tumour adaptive immunity’ in both pre-clinical as well as clinical settings. Although the ability of PDT to induce ‘anti-cancer vaccine effect’ is still debatable, yet it has been shown to be capable of inducing exposure/release of certain damage-associated molecular patterns (DAMPs) like HSP70. Therefore, it seems that PDT is unique among other approved therapeutic procedures in generating a microenvironment suitable for development of systemic anti-tumour immunity. Apart from this, recent times have seen the emergence of certain promising modalities based on PDT like-photoimmunotherapy and PDT-based cancer vaccines. This review mainly discusses the effects exerted by PDT on cancer cells, immune cells as well as tumour microenvironment in terms of anti-tumour immunity. The ability of PDT to expose/release DAMPs and the future perspectives of this paradigm have also been discussed.

Photodynamic therapy: illuminating the road from cell death towards anti-tumour immunity

Neutrophils play an important role in the efficacy of photodynamic therapy (PDT). These leukocytes rapidly accumulate into the tumor lesion after PDT and most likely eradicate the remaining attenuated tumor cells. The underlying mechanism of the accumulation of neutrophils at the time of PDT is not known. Therefore, we determined the effect of PDT on the course of mature and immature neutrophils in the circulation of rhabdomyosarcoma-bearing rats and studied the changes in the level of interleukin (IL)-1β as an important stimulator of the proliferation of precursor cells of the granulocyte lineage in the bone marrow. We found that the effect of PDT on tumor growth was preceded by a rapid and specific increase of the number of mature neutrophils in the peripheral blood as early as 4 h after the start of PDT treatment and reaching maximum values after 8 h. At 24 h, the neutrophil numbers in the PDT-treated rats were still elevated as compared to sham-treated rats. In sham-treated rats, the numbers of blood monocytes and lymphocytes decreased by about 50% after 2 h and returned to their normal levels as soon as 2 h later. In PDT-treated rats, the course of monocyte numbers showed a similar pattern; however, lymphocyte numbers did not reach the normal range until 24 h. The specific increment of neutrophils was preceded by an increase of band neutrophil numbers and elevated serum levels of IL-1β which were maximal at 2 h after the start of PDT. Pearson correlation analysis showed a significant association between the serum levels of IL-1β at this time point and the number of band neutrophils at 4 h (R2 = 0.58; P = 0.03) and the number of mature neutrophils at 8 h (R2 = 0.54; P = 0.04). This suggests that PDT evoked an IL-1-dependent increased production rate of neutrophils in the bone marrow. Further investigation showed that the injection of anti-granulocyte colony-stimulating factor (G-CSF) antibodies not only attenuated the increase in neutrophil numbers but also greatly decreased the efficacy of PDT. On this basis, we suppose that an IL-1-induced release of G-CSF by PDT underlies this nonspecific immune reaction to the tumor. Apparently, G-CSF not only stimulates the production rate of neutrophils in the bone marrow but also increases the functional activity of these leukocytes to become indispensable tumor cell killers.

https://cancerres.aacrjournals.org/content/canres/57/13/2555.full.pdf

Role of interleukin 1 and granulocyte colony-stimulating factor in photofrin-based photodynamic therapy of rat rhabdomyosarcoma tumors.

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Role of interleukin 1 and granulocyte colony-stimulating factor in photofrin-based photodynamic therapy of rat rhabdomyosarcoma tumors.